This invention relates to methods and apparatus for lead placement and other related procedures on or in connection with the heart.
Leads are conductive devices or electrodes for temporary or permanent contact or implantation on a heart surface. Leads are well known in the art and commonly have an elongated shape and include a distal end, typically with an electrode alone or in combination with a retention member, such as spiral or barbed, located thereon for attachment to the desired heart surface.
Leads carry electrical signals to and from the heart for a variety of purposes. One purpose, among many, of lead implantation is to allow pacing of the heart so as to restore the normal sequence of mechanical contractions to the heart. By way of example, but not limitation, leads may be placed on a surface of the heart in conjunction with a biventricular pacemaker, which generates a pacing signal. A proximal end of the lead is connected to the pacemaker while the distal end of the lead is attached to the desired heart location to carry the electrical signal to the heart. Temporary leads may also be used to monitor heart performance, to “map” the heart to identify conductive pathways, to identify sources of aberrant electrical pulses and to carry out various other diagnostic and/or therapeutic procedures.
A myriad of lead implantation sites relative to treatment of the human heart are also possible. Leads may be placed on an outer (epicardial) surface of the heart, implanted within the heart on an interior (endocardial) heart surface, or placed within the coronary sinus. The human heart is generally situated in a multi-layer membrane or heart sac, commonly known as the pericardium. The space between the pericardium and the outer or epicardial surface of the heart is commonly called the pericardial space. Although it may be technically possible to place leads on the outer surface of the pericardium, it is preferred to place leads within the pericardial space so as to improve the conductivity of the electrical path between the lead and the selected heart tissue.
Current apparatus and methods for epicardial lead placement often utilize non-minimally invasive medical procedures. These methods may involve a large incision into the chest, thoracotomy or medial sternotomy of a patient and/or opening of the chest cavity for access to the heart. These procedures typically may require the patient to be generally anesthetized, selectively intubated with collapse of a lung. A further major disadvantage of these procedures is that they may require a chest tube following surgery and are often associated with a painful postoperative course.
Sub-xyphoid access to the heart surfaces has been previously proposed by one of the inventors here in U.S. patent application Ser. No. 09/315,601 filed May 20, 1999 and is incorporated by reference herein. One potential difficulty which needs to be overcome when using the sub-xyphoid route for lead placement is the need for a substantial distal portion of the lead to be orthogonally disposed relative to the selected lead placement site in order to adequately attached the lead on the heart surface. In other words, it has been previously considered that the incident angle of approach of the lead placement apparatus should be disposed at a nearly perpendicular angle relative to the heart surface in order to position the distal outlet in a desired direction for lead placement. Because the angle of approach is so large, it requires a large working volume within the pericardial space. The working space required by the apparatus thus displaces a greater amount of cardiac tissue, which can increase the risk of complications during and after surgery. Therefore, there is a need for apparatus and methods for lead placement which avoid these shortcomings.
Several devices and methods for minimally invasive access to the epicardial surface of the human heart have been described in co-pending applications Ser. Nos. 09/315,601 filed May 20, 1999, and Ser. No. 09/397,392 filed Sep. 16, 1999, both of these applications are hereby incorporated by reference in the present application.
Another drawback of current lead placement apparatus and methods is that they do not typically incorporate the ability to navigate over the surfaces of the heart for optimal lead placement. In one aspect, it would be desirable to provide an apparatus which permits temporary pacing of the heart so as to determine the optimal lead placement site prior to attachment of the lead to the heart surface. Pacing by temporary electrodes or leads prior to attachment of a permanent lead better ensures that the lead is properly attached to the desired heart location. In another aspect, it would be desirable to have a lead placement apparatus which prevents lead deposition in proximity to a coronary artery. Since coronary arteries surround the exterior of the heart, there is a danger that lead implantation could pierce the artery, resulting in possible bleeding into the pericardial space which may lead to hemodynamic compromise and collapse. Placement of an epicardial lead onto a coronary artery may occlude the artery resulting in infarction of the myocardium perfused by that artery. So, it would be desirable to provide a lead placement apparatus which has the ability to sense when the lead placement apparatus is unduly close to a coronary artery.
Current lead placement devices also do not provide relative positioning of the distal end of the device so as to orient the distal end in the desired direction for lead placement. Since the surface of the heart is not flat or uniform, the ability to position the distal end against the desired lead placement location is also desirable. Even once the lead placement site is located, the lead placement apparatus desirably should facilitate lead removal from the apparatus.
Accordingly, it is a general object of the present invention to provide a minimally invasive method and apparatus for placing a lead on a surface of the heart.
Another object of the present invention is to provide for an apparatus and method for lead placement, which apparatus has a geometry specifically suited for lead placement.
It is the object of another aspect of the present invention to provide a method and apparatus for temporary pacing of the heart prior to lead placement or in connection with mapping the conductive pathways of the heart tissue.
It is another object of the present invention to provide a method and apparatus for detecting proximity to the coronary arteries so as to avoid placement of the lead on or near a coronary artery.
It is a further object of the present invention to provide a method and apparatus which provides a distal end of the apparatus which is adapted to move in at least one plane when force is applied to the apparatus.
It is yet another object of the present invention to provide a method and apparatus having an expandible member to hold the apparatus adjacent the epicardial surface for lead placement.
A further object of the present invention is to provide a lead placement apparatus which facilitates lead removal.
A yet further object of the present invention is to provide a minimally invasive lead placement apparatus having a distal end portion which has an acute angle relative to the longitudinal axis for lead placement.
These objectives are provided to illustrate the context of the present invention and are not an exclusive listing of the objectives or benefits of the present invention. Not all of these objectives are necessarily met in each apparatus or method of the present invention. Apparatus or methods of the present invention may meet or address one or more, but less than all, of these objects or other objects or benefits of the invention apparent in other parts of this description. Therefore, these objectives are not presented for, and should not be used for, the purpose of limiting the scope of the invention as set forth in the appended claims.